Broadband connectivity products provide the physical contact points needed to connect different communications network elements and gain access to communications system circuits for the purposes of installing, testing, monitoring, accessing, managing, reconfiguring, splitting and multiplexing such circuits within service providers' serving offices and the last mile/kilometer portion of communications networks. These products include broadband connection and access devices for copper, coaxial cable, optical, wireless and broadcast communications networks.
The enhancement of broadband connectivity is a perpetual goal of the communications industry. As raw speeds of large-scale and personal computing devices soar, the tremendous increase in data transmission demands continue to push the networking bandwidth envelope to capacity. Technological advances, together with the ever-increasing demand for communicating bandwidth-intensive multimedia content, continually fuel the unrelenting bandwidth dilemma. As the demand for bandwidth escalates, the need for high-bandwidth broadband systems commensurately increases.
The term “broadband” has often been used to describe high-bandwidth transmission of data signals, such as data, video, voice, video conferencing, etc. Broadband philosophies often address networking principles applicable to the backbone of the networking system, since the networking backbone generally faces the highest bandwidth demands. There are many competing technologies for delivering broadband access. For example, there are a number of standards used in digital telecommunications, including TCP/IP (Transmission Control Protocol/Internet Protocol), Ethernet, HDLC (High-level Data Link Control), ISDN (Integrated Services Digital Network), ATM (Asynchronous Transfer Mode), X.25, Frame Relay, Digital Data Service, FDDI (Fiber Distributed Data Interface), T1, xDSL (x Digital Subscriber Line), Wireless, Cable Modems, and Satellite among others.
Many of these standards employ different packet and/or frame formats. The term “frame” is often used in reference to encapsulated data at OSI layer 2, including a destination address, control bits for flow control, the data or payload, and CRC (cyclic redundancy check) data for error checking. The term “packet” is often used in reference to encapsulated data at OSI layer 3. Further, the term “cell” is often used in reference to a group of bytes/octets conditioned for transmission across a network. However, it should be understood that for purposes of the present application, the terms packet, frame, and cell may be used interchangeably to refer to groups or collections of data. Further, a packet format or frame format generally refers to how data is encapsulated with various fields and headers for transmission across the network. For example, a data packet typically includes a destination address field, a length field, an error correcting code (ECC) field or cyclic redundancy check (CRC) field, as well as headers and trailers to identify the beginning and end of the packet. The terms “packet format” and “frame format” also referred to as “cell format” are generally synonymous for purposes of this application.
Packets transmitted across a network are associated with a transmission protocol. A protocol is a set of rules that governs how devices on a network exchange information. Packets traversing the network may be of differing formats or protocols. Examples of typical protocols used to communicate information include the Internet Protocol (IP), which is a “best-effort,” connectionless protocol responsible for delivering data from host to host across a network such as the Internet. IP is a predominant protocol used to transmit data across the Internet.
Other protocols are used to transmit packets across the Internet as well, such as Framed ATM over SONET/SDH Transport (FAST) and IP on multiprotocol label switching (MPLS). FAST is a new protocol intended to improve the performance of asynchronous transfer mode (ATM). FAST introduces a variable length user data field, while preserving the proven advantages of ATM, such as real quality of service guarantees, the security and traffic isolation provided by virtual connections, network management, traffic management, control mechanisms for bandwidth on demand, etc. MPLS integrates layer-2 information about network links into layer-3 (IP) within a particular autonomous system in order to simplify and improve IP-packet exchange. MPLS essentially provides connection-oriented labeling in an otherwise connectionless environment. With MPLS, different flows can be classified, and different service levels can be associated with the different flow classifications.
As described above, packets transmitted on a network such as the Internet may be associated with one of a number of different protocols, and thus packets associated with different protocols may be received at a given node, switch, router, etc. The introduction of multiple packet protocols at a node may require special consideration when the entire data flow is subject to editing as the packets traverse the network. For example, fairness with variable sized packets, redundancy and failover mechanisms for high availability applications must be supported.
Redundancy has often been solved by using SONET rings for telecommunications networks, and routing protocols and hot standby routers for routers in Internet networks. SONET rings include rings of fiber so that if the fiber is cut at any one location the data can travel the other direction on the ring. SONET rings have been used for traditional telecom applications, but do not lend themselves well to data oriented networks as most of the data implementations are a meshed configuration of routers not a series of add drop multiplexers on a SONET ring.
Providing fast recovery for routers or switches in a meshed configuration is required for the data networks to achieve the same reliability of the traditional telecom networks. This problem has been solved in the past by relying on the routing protocols to detect a failed link and recover and/or to have a hot standby router to switch over to should the link or the router fail. However, reliance on the routing protocols does not provide fast enough recovery and hot standby routers are a costly solution because duplicate routers are required in the system. Accordingly, there is a need for routers and switches to be able to instantaneously direct the flow of traffic to another port should there be a failure on a link.
The convergence of the telecommunications and data networks has put the burden on systems to also provide multiple service classes to differentiate the traffic that is on the network. Traditionally the telecommunications networks have been a statistical multiplexing hierarchy that provided connection oriented circuits for guaranteed bandwidth. The data networks have traditionally used best effort services providing all packets the same service in a connectionless best effort manner. As the transport speeds keep increasing there is an expansion in the types of traffic on each transport link. Therefore, the devices that are terminating high-speed transport links need the ability to separate and classify each of the service classes and process them according to the service guarantees.
There are a number of emerging protocols to address the problem of providing differentiated service such as MPLS, RSVP and Diff-Serv. To implement these protocols the entire end-to-end system must be aware of different service levels and to provide them in the form of bandwidth, latency and jitter parameters.
The merging of best effort traffic and statistical multiplexed traffic is required by the system vendors to effectively implement the emerging protocols. This problem is greatly aggravated by variable length packets, burstiness of the Internet coupled with the demands of voice and video traffic. The mixing of short and long packets increases the difficulty in providing jitter and latency guarantees. Accordingly, there is a need for a solution to provide multiple service classes through a router or switch interconnecting high-speed transport links.
Multicast is another important technology for distributing broadband services through data networks. The ability of switches and routers to multicast a packet greatly reduces the amount of traffic distributed on upstream networks.
There are many issues in deploying large multicast networks. The throughput of today's routers for multicast is severely limited. Multicast by its nature is a difficult problem and requires efficient hardware to enable effective multicast solutions. Actual multicast throughput may only be 5% to 10% of capacity due to inefficient support for multicast. The Internet Engineering Task Force (IETF) has dedicated experimental networks for multicast applications.
There are two basic mechanisms from replicating a multicast packet. The first is to put the packet into memory and then retrieve it multiple times. The second method is to use multiplexers to duplicate the packet in real time, such as in a crossbar switch. The first solution reduces the amount of memory bandwidth by the number of times it is to be replicated thereby making it costly for large multicast applications. The second approach does not reduce the throughput as the packets are duplicated in real time. However the burden is on the system to ensure that there is no contention for the destinations before the replication occurs. The arbitration for the available destination and waiting for 1 of the destinations to free can and will significantly reduce throughput for multicast traffic. Thus, there is a need for a system that efficiently handles multicast traffic.
It can be seen then that there is a need for a multi-service queuing method and apparatus that provides exhaustive arbitration, load balancing, support for rapid port failover and efficient multicast.